Question: Omar did 28 fewer push-ups than Tiffany in the evening. Tiffany did 39 push-ups. How many push-ups did Omar do?
Answer: Tiffany did 39 push-ups, and Omar did 28 fewer than that, so find the difference. The difference is $39 - 28$ push-ups. She did $39 - 28 = 11$ push-ups.